1. Field of the Invention
The present invention generally relates to brake apparatus for railway vehicles and, more particular, to a service portion of a brake control valve.
2. Description of Related Art
China Railways have a standardized pneumatic air brake valve, called “Type 120”, which is similar in overall operation to American Association of Railroads (AAR) pneumatic air brake valves (such as the WABCO ABD), with a pipe bracket, service portion, and emergency valve. The main operating difference between the Type 120 and the ABD and related AAR valves is that the emergency portion provides only vent valve functions, and still relies on the service portion to move air from the reservoir to the brake cylinder. Further, there is no difference in brake cylinder equalization pressure between full service and emergency modes. The pipe bracket also differs from a mechanical viewpoint, with different mounting dimensions.
The Type 120 braking systems utilized in China are generally pneumatic. However, Electronically Controlled Pneumatics (ECP) braking systems are becoming more widely used, and offer many advantages over pneumatic equipment. Having the ability to apply ECP equipment to railcars is generally desirable to take advantage of the superior braking and safety capabilities offered by ECP equipment. The ECP brake equipment on each rail vehicle typically includes a Car ID (CID) which interfaces to the ECP trainline, Car Control Unit (CCD), and ECP Manifold. The ECP Manifold contains the pressure transducers, various pneumatic and electro-pneumatic valves, etc. This equipment is used to monitor the pressures in the brake pipe, the brake cylinder(s), and specific reservoirs, and convert the electrical brake commands into a form usable by the microprocessor. Operating according to its programming code and to the dictates of the brake commands and other electrical signals it has received, the microprocessor controls the electro-pneumatic valves in a manner well-known in the brake control art.
The ECP Manifold also includes at least one microprocessor with a serial data and power interface to the CCD. However, the ECP Manifold functions can also be performed without a microprocessor, based upon direct interface from the CCD to each of the electro-pneumatic solenoid valves and pressure transducers. Further, ECP equipment allows the railcar to be operated in the strictly pneumatic mode if desired, or in the event of a loss of power to the ECP equipment.